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Larry,
Gempak provides the following in the gemlib:
FUNCTION PR_PMSL ( pres, tmpc, dwpc, selv )
C************************************************************************
C* PR_PMSL *
C* *
C* This function computes PMSL from PRES, TMPC, DWPC, and SELV. The *
C* following equation is used: *
C* *
C* PMSL = PRES * EXP ( ( GRAVTY * SELV ) / ( RDGAS * TVAVE ) ) *
C* *
C* TVAVE = avg virtual temp between station and sea level *
C* = TVRK + ( DELTV / 2 ) *
C* DELTV = GAMUSD * SELV / 1000 *
C* *
C* Wallace and Hobbs. *
C* *
I found the Wallace and Hobbs reference in my copy,
Atmospheric Science: an introductory survey, 1977 eq 2.31. Page 59.
So, if you like Fortran, you can just call that routine.
Steve Chiswell
Unidata User Support